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Researchers estimate that 50 percent of the general population is at risk of vitamin D deficiency and insufficiency, and this percentage rises in higher-risk populations such as the elderly and those with darker skin

Signs you may have a vitamin D deficiency include age over 50, having darker skin, obesity, achy bones, feeling blue, head sweating, and gut trouble

Increasing levels of vitamin D3 among the general population could prevent chronic diseases that claim nearly one million lives throughout the world each year

Vitamin D deficiency is incredibly common in the US, but many Americans mistakenly believe they aren't at risk because they consume vitamin-D-fortified foods (such as milk). There are very few foods that actually have therapeutic levels of vitamin D naturally and even fortified foods do not contain enough vitamin D to support your health needs. Despite its name, vitamin D is not a regular vitamin. It's actually a steroid hormone that you are designed to obtain primarily through sun exposure, not via your diet.

Just How Widespread Is Vitamin D Deficiency?

Before the year 2000, very few doctors ever considered the possibility that you might be vitamin D deficient. But as the technology to measure vitamin D became inexpensive and widely available, more and more studies were done, and it became increasingly clear that vitamin D deficiency was absolutely rampant. For example, according to one of the leading vitamin D researchers, Dr. Michael Holick:

• The Centers for Disease Control and Prevention (CDC) reported that 32 percent of children and adults throughout the US were vitamin D deficient -- and this is grossly underestimated as they used vitamin D levels that were not consistent with optimal health.

• The National Health and Nutrition Examination Survey found that 50 percent of children aged one to five years, and 70 percent of children between the ages of six and 11, are deficient or insufficient in vitamin D

• Researchers such as Dr. Holick estimate that 50 percent of the general population is at risk of vitamin D deficiency and insufficiency

Researchers have also noted that vitamin D deficiency is prevalent in adults of all ages who always wear sun protection (which blocks vitamin D production) or limit their outdoor activities.1 People with increased skin pigmentation (such as those whose ancestors are from Africa, the Middle East, or India) are also at risk, as are the elderly.

It's estimated that over 95 percent of US senior citizens may be deficient in vitamin D, not only because they tend to spend a lot of time indoors but also because they produce less in response to sun exposure (a person over the age of 70 produces about 30 percent less vitamin D than a younger person with the same sun exposure).2

7 Signs You May Be Vitamin D Deficient

The only way to know for sure if you're vitamin D deficient is via blood testing. However, there are some signs and symptoms to be aware of as well. If any of the following apply to you, you should get your vitamin D levels tested sooner rather than later.

1. You Have Darker Skin — African Americans are at greater risk of vitamin D deficiency, because if you have dark skin, you may need as much as 10 times more sun exposure to produce the same amount of vitamin D as a person with pale skin! As Dr. Holick explained, your skin pigment acts as a natural sunscreen, so the more pigment you have, the more time you'll need to spend in the sun to make adequate amounts of vitamin D.

2. You Feel "Blue" — Serotonin, the brain hormone associated with mood elevation, rises with exposure to bright light and falls with decreased sun exposure. In 2006, scientists evaluated the effects of vitamin D on the mental health of 80 elderly patients and found those with the lowest levels of vitamin D were 11 times more prone to be depressed than those who received healthy doses.3

3. You're 50 or Older — As mentioned, as you get older your skin doesn't make as much vitamin D in response to sun exposure. At the same time, your kidneys become less efficient at converting vitamin D into the form used by your body and older adults tend to spend more time indoors (i.e. getting even less sun exposure and therefore vitamin D).

4. You're Overweight or Obese (or Have a Higher Muscle Mass) — Vitamin D is a fat-soluble, hormone-like vitamin, which means body fat acts as a "sink" by collecting it. If you're overweight or obese, you're therefore likely going to need more vitamin D than a slimmer person -- and the same holds true for people with higher body weights due to muscle mass.

5. Your Bones Ache — According to Dr. Holick, many who see their doctor for aches and pains, especially in combination with fatigue, end up being misdiagnosed as having fibromyalgia or chronic fatigue syndrome.

"Many of these symptoms are classic signs of vitamin D deficiency osteomalacia, which is different from the vitamin D deficiency that causes osteoporosis in adults," he says. "What's happening is that the vitamin D deficiency causes a defect in putting calcium into the collagen matrix into your skeleton. As a result, you have throbbing, aching bone pain."

6. Head Sweating — According to Dr. Holick, one of the first, classic signs of vitamin D deficiency is a sweaty head. In fact, physicians used to ask new mothers about head sweating in their newborns for this very reason. Excessive sweating in newborns due to neuromuscular irritability is still described as a common, early symptom of vitamin D deficiency.4

7. You Have Gut Trouble — Remember, vitamin D is a fat-soluble vitamin, which means if you have a gastrointestinal condition that affects your ability to absorb fat, you may have lower absorption of fat-soluble vitamins like vitamin D as well. This includes gut conditions like Crohn's, celiac and non-celiac gluten sensitivity, and inflammatory bowel disease.

Researchers have pointed out that increasing levels of vitamin D3 among the general population could prevent chronic diseases that claim nearly one million lives throughout the world each year. Incidence of several types of cancer could also be slashed in half. As mentioned by Dr. Holick, one of the Nurses' Health Studies showed that nurses who had the highest blood levels of 25-hydroxyvitamin D, averaging about 50 ng/ml, reduced their risk of developing breast cancer by as much as 50 percent. Similarly, a Canadian study done by Dr. Knight showed that women who reported having the most sun exposure as a teenager and young adult had almost a 70 percent reduced risk of developing breast cancer. Dr. Holick noted:

"Studies have shown that if you improve your vitamin D status, it reduces risk of colorectal cancer, prostate cancer, and a whole host of other deadly cancers by 30 to 50 percent. You're correct. Cancer is a big deal. You need to realize that vitamin D is playing a very important role in helping to maintain cell growth and to help fight cancer when a cancer cell is developing in your body."

Vitamin D also fights infections, including colds and the flu, as it regulates the expression of genes that influence your immune system to attack and destroy bacteria and viruses. In this interview above, Dr. Holick expounds on these and many other health benefits of vitamin D. For instance, optimizing your vitamin D levels can help protect against:

• Cardiovascular disease. Vitamin D is very important for reducing hypertension, atherosclerotic heart disease, heart attack, and stroke. According to Dr. Holick, one study showed that vitamin D deficiency increased the risk of heart attack by 50 percent. What's worse, if you have a heart attack and you're vitamin D deficient, your risk of dying from that heart attack creeps up to nearly 100 percent!

• Autoimmune diseases. Vitamin D is a potent immune modulator, making it very important for the prevention of autoimmune diseases, like multiple sclerosis and inflammatory bowel disease.

• Infections, including influenza. It also helps you fight infections of all kinds. A study done in Japan, for example, showed that schoolchildren taking 1,200 units of vitamin D per day during winter reduced their risk of getting influenza A infection by about 40 percent. I believe it's far more prudent, safer, less expensive, and most importantly, far more effective to optimize your vitamin D levels than to get vaccinated against the flu.

• DNA repair and metabolic processes. One of Dr. Holick's studies showed that healthy volunteers taking 2,000 IUs of vitamin D per day for a few months up-regulated 291 different genes that control up to 80 different metabolic processes, from improving DNA repair to having effect on autoxidation (oxidation that occurs in the presence of oxygen and/or UV radiation, which has implications for aging and cancer, for example), boosting your immune system and many other biological processes.

How Much Vitamin D Do You Need for Optimal Health?

When it comes to vitamin D, you don't want to be in the "average" or "normal" range, you want to be in the "optimal" range. The reason for this is that as the years have gone by, researchers have progressively moved that range upward.

At present, based on the evaluation of healthy populations that get plenty of natural sun exposure, the optimal range for general health appears to be somewhere between 50 and 70 ng/ml. As for how to optimize your vitamin D levels, I firmly believe that appropriate sun exposure is the best way. In fact, I personally have not taken a vitamin D supplement for three or four years, yet my levels are in the 70 ng/ml range.

Generally speaking, this will be when your skin turns the lightest shade of pink or, as Dr. Holick recommends, about half of the time you suspect it would take you to get a mild sunburn (So if you know you tend to get sunburned after 30 minutes, you'd want to stay in the sun for about 15 minutes). How long you need to stay in the sun varies greatly depending on the factors below:

Antioxidant levels and diet in general

Age

Skin color and/or current tan level

Use of sunscreen

Latitude and altitude (elevation)

Cloud cover and pollution

Ozone layer

Surface reflection

Season

Time of day

Weigh

If your circumstances don't allow you to access the sun, then you really only have one option if you want to raise your vitamin D, and that is to take a vitamin D supplement. As a general guideline, research by GrassrootsHealth suggests that adults need about 8,000 IUs per day to achieve a serum level of 40 ng/ml. If you do opt for a vitamin D supplement, please remember that you also need to boost your intake of vitamin K2 through food and/or a supplement.

If you're getting your vitamin D from the sun, this is not as critical, although you'd be wise to make sure you're getting sufficient amounts of vitamin K2 from your diet either way.

Get Your Vitamin D Levels Tested with the D*Action Project

How do you know if your vitamin D level is in the right range? The most important factor is having your vitamin D serum level tested every six months, as people vary widely in their response to ultraviolet exposure or oral D3 supplementation. The test is called 25(OH)D, also called 25-hydroxyvitamin D, and you can have it done by virtually any physician.

You should test at your highest point, which (if you live in the US) is typically in August and again at your lowest point, which is usually February. Knowing your vitamin D levels is one of the most important tests you can take, so please, if you haven't checked your levels before, do it now -- I cannot stress the importance of this enough.

If you're interested in having your vitamin D levels tested right from home, consider joining the D*Action Project. The D*Action project has been initiated by GrassrootsHealth along with 42 leading vitamin D researchers to demonstrate how health can be achieved right now with what's known about vitamin D with a combination of vitamin D measurement and health outcome tracking. In order to spread this health movement to more communities, the project needs your involvement.

To participate, simply purchase the D*Action Measurement Kit and follow the registration instructions included. (Please note that 100 percent of the proceeds from the kits go to fund the research project. I do not charge a single dime as a distributor of the test kits.)

As a participant, you agree to test your vitamin D levels twice a year during a five-year study, and share your health status to demonstrate the public health impact of this nutrient. There is a $65 fee every six months for your sponsorship of this research project, which includes a test kit to be used at home, and electronic reports on your ongoing progress. You will get a follow up email every six months reminding you "it's time for your next test and health survey."

Remember, more than 75 percent of the world's population is vitamin D deficient and most don't know it! GrassrootsHealth D*Action is an integrated set of performance and feedback systems to give you complete control of your individual vitamin D performance systems, which will help you gain a total picture of your health. There's no doubt in my mind that the D*Action programs can be a major key to help turn the current health paradigm from "treatment" to "prevention."

Disclaimer: The entire contents of this website are based upon the opinions of Dr. Mercola, unless otherwise noted. Individual articles are based upon the opinions of the respective author, who retains copyright as marked. The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. It is intended as a sharing of knowledge and information from the research and experience of Dr. Mercola and his community. Dr. Mercola encourages you to make your own health care decisions based upon your research and in partnership with a qualified health care professional. If you are pregnant, nursing, taking medication, or have a medical condition, consult your health care professional before using products based on this content.

If you want to use an article on your site please click here. This content may be copied in full, with copyright, contact, creation and information intact, without specific permission, when used only in a not-for-profit format. If any other use is desired, permission in writing from Dr. Mercola is required.

Disclaimer: The entire contents of this website are based upon the opinions of Dr. Mercola, unless otherwise noted. Individual articles are based upon the opinions of the respective author, who retains copyright as marked. The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. It is intended as a sharing of knowledge and information from the research and experience of Dr. Mercola and his community. Dr. Mercola encourages you to make your own health care decisions based upon your research and in partnership with a qualified health care professional. If you are pregnant, nursing, taking medication, or have a medical condition, consult your health care professional before using products based on this content.

If you want to use an article on your site please click here. This content may be copied in full, with copyright, contact, creation and information intact, without specific permission, when used only in a not-for-profit format. If any other use is desired, permission in writing from Dr. Mercola is required.